Acoustic cavitation assisted synthesis of PCDs@PVA composite film for UV shielding, intelligent pH detection, information encryption and food packing applications

Excessive exposure to UV and high-energy blue light (HEBL) can severely damage the skin and eyes. Therefore, it is essential to protect our bodies from UV and HEBL radiation. We created PEG-derived carbon dots (PCDs) using the acoustic cavitation approach in order to completely block UV and HEBL. The influence of different experimental parameters such as sonication time, amplitude, and temperature on the PCDs is examined. The optimized PCDs are found to have an average diameter ranging from 5 to 9 nm, contingent upon the preparation circumstances, and to have a quantum yield (QY) of 14–16 %. The PCDs vivid colour and simultaneous UV and HEBL absorption properties allowed the PVA film containing 0.120 wt% of PCDs to demonstrate outstanding blocking efficiency, with 99.9 % blocking in HEBL and 100 % blocking in UV-C, UV-B, and UV-A. The photoluminescence (PL) behaviour of PCDs is greatly reduced by Fe³⁺ ions because of strong excited state electron transfer. This fluorescent “turn-off” behaviour towards Fe³⁺ is highly selective and sensitive with a limit of detection (LoD) of 0.366 μM. Paper-based sensors incorporating PCDs are developed for the rapid and accurate detection of Fe³⁺ in surface water, wastewater treatment plant effluent, and tap water, leveraging their excellent sensitivity and selectivity towards Fe³⁺. The characteristics of ink-free patterned substrates are displayed by PCDs scattered across a PVA matrix, which makes them useful for the non-destructive acquisition and recognition of latent fingerprints (LFPs). A flexible, transparent film is produced when a LFP is exposed to a PCDs@PVA solution. In this film, a steady luminous fingerprint with specific ridge characteristics that aid in personal recognition is seen. This method shows promise for lifting and identifying long-exposed LFPs from various surfaces without causing damage. It is believed that the interfacial segregation of PCDs inside the PVA matrix during the film production process serves as a mechanism for LFP collection and visualization. The YOLOv8x program, which utilizes deep convolutional neural networks, is employed to analyze the discernible features present in fingerprints (FPs). Notably, their exceptional flexibility, foldability, and sustainability create new opportunities for use in the anti-counterfeiting (AC) field. Because of its remarkable fluorescence stability, it may be a viable substitute for conventional fluorescent inks. Fresh green apples are observed over time after being coated with 0.120 wt% PCDs@PVA and PVA. Virtual assessments indicated that the 0.120 wt% PCDs@PVA film coating significantly reduced weight and moisture loss, effectively inhibiting fungal growth and spoilage for over 25 days at room temperature (RT). Overall, the results clearly show that the PCDs@PVA film is easy to make, flexible, safe for the environment, and resistant to photodegradation. Hemolysis, and blood clotting exhibited favorable biocompatibility and nontoxicity.